Backflow prevention device



Dec. 9, 1952 D. G. GRlswoLD BACKFLOW PREVENTION DEVICE 15 sheets-sheet 1Filed May 2l, 1945 Dec. 9, 1952 p. ca. GRlswoLD I 2,620,816

BCKFLOW PREVENTION DEVICE .Filed May 21, 1945 l5 Sheets-Sheet 2 Dec. 9,1952 D. G. GRlswoLD BAcxFLow PREVENTVIQN DEVICE Filed May 2l, 1945 15.ShetS-Sheeb 3 Dec. 9, 1952 D. G. GRlswoLQ '2,620,816

y BACKFLOW RJENToN DEVICEv A Filed May 21, 1945 I 154 sheets-shew 4az'mE/-d @www ama/aufm Dec. 9, l952 D. G. GRlswoLD 2,620,816 BAQKF'LOWPREVENTION DEVICE Filed May 21, 1945 15 Sheets-Sheet 5 www@ Dec. 9, 1952D. G. GRlswoLn 2,620,816

' BAcxFjLow PREVENTIQN DEVICE Filed May 21, 1945 V 'v 15` Sheets-Sheet 6272 234 242 SYM/Wm 29a gald. 5113200@ @www Dec. .9, 1952 ACKFLOWPREVENTION DEVICE Filed May 2l, 1945 l5 Smets-Sheet '7 Dec. 9, 1952 p.G. GRxswoLo 2,620,816

l BACKFLow PREvENTIo'N isvrcrav Filed may 21, 1945A 15 sheets-sheet 8Syvum/mw @www D. G. GRlsw-OLD BAcxFLow PREVENTION DEVICE Dec. 9, 1952Filed May 21, 1945 l5 Sheeigs-Sheet 9 Dec. 9, 1952 D. G. GmswoLDBACKFLOW PRVENTION DEVICE l5 Sheets-Sheet 1 0 Filed May 21, 1945 ZQZ@MES@ DWWOJO ald l' Dec. 9, 1952 D. G. GRlswoLD BACKFLOW PREVENTIONDEVICE l5 Sheets-Sheet ll Filed May 2l, 1945 EWS bv atto/WIW Dec. 9,1952 D. G. GRlswoLp BACKFLOW PREVENTION DEVICE 15`Sheets-Sheet l2 FiledMay 21, 1945 L1 Wl-- Dec. 9, 1952 n. G. csmsWoLD 2,620,816

BACKFLOW PREVENTION DEVICE Filed May 21, 1945 -15 Sheets-Sheet 13 Dec.9, 1952 D. G. GRlswol- D 2,520,816

BACKFLOW PREVENTION DEVICE Filed May 21, 1945 15 Sheets-Sheet 15 olza/dnkwold a NQ: my

Patented Dec. 9, 1952 UNITED STATES PATENT OFFICE BACKFLOW PREVENTIONDEVICE Donald G. Griswold, Alhambra, Calif.

,.-l.pplication May 21, 1945, Serial No. 595,007

30 Claims.

The present invention relates to backflow protection or preventiondevices adapted to prevent contamination of public Water distributionsystems supplying drinking water to dwellings, hotels, factories,Shipyards, public buildings, etc.

During recent years, sanitary engineers and health authorities have morefully recognized the importance of protecting public water supplysystems against contamination resulting from cross connections andbackflow or back-siphonage; that is, the pollution of the water supplyby unpotable water nding its Way into the city Water mains from theconsumers property as the result of cross connections or backiiowbetween contaminated Water and potable water sources. Many epidemics ofamoebic dysentery and other ailments yhave been directly traced topolluted water supply systems, thus emphasizing the great importance ofproviding adequate and positive safeguards.

While previous attention had been given to the problem of backflowprevention, no device representing a complete solution to the manyphases of the problem was produced, and the present invention waspurposely developed to meet the many objections to prior backflowprevention devices and to overcome the many known difliculties that haveconfronted health officers, sanitary engineers and others concerned withthe problem of supplying unpolluted Water to consumers.

Accordingly, the principal object of the invention is to provide backowprevention means which meets and complies with all known sanitationrequirements.

Another object of the invention is to pl'ovide dependable backflowprotection means which will positively prevent all return-now of watertherethrough from the consumers pipe system to the water supply mains.

A more specic object of the invention is to provide a backow preventiondevice which Will preclude back-Siphoning of Water from the consumerspipe system through the backow prevention device and into the supplymain when a vacuum condition occurs in said supply main.

Another specific object of the invention is to provide a water supplyprotection unit which will preclude back-flow therethrough in the eventthat the check valve at the consumers or service end of the unitdevelops a leak.

Another important object of the invention is to provide a backowprevention unit including check valve means which will immediately closewhen a static condition occurs in the line and before any tendency forbacklow in the line arises.

Another object of the invention is to provide a backiow prevention unitincluding valve means which will close by gravity when the pressure atthe supply end of the unit is approximately equal to that at the serviceend of the unit, and which valve means is positively held closed byoperating fluid under pressure in the event that the pressure at theservice side of the unit becomes greater than that at the supply side ofsaid unit.

Another object of the invention is to provide backflovv protection meanswhich is vented to the atmosphere to prevent flow therethrough in theevent that the pressure on the service side of said unit exceeds thepressure on the supply side of said unit.

Another object of the invention is to provide a backiiow prevention unitincluding "power-operated, or iiuid pressure operated, valve meansarranged to automatically close by gravity during a static linecondition and to be positively held closed by operating fluid underpressure during a line condition tending to create a backow.

Another object of the invention is to provide a backflow prevention unitincluding a plurality of check valves and means responsive to thedifferential pressure across said check valves for controlling theoperation of at least the check valve at the supply end of said unit.

Another object of the invention is to provide a backiiow prevention unitincluding a plurality of valves, at least one of which is operated byiiuid under pressure, and a fluid pressure-responsive control device forsaid valve subject to the differential pressure across said valves andincluding means for preventing ley-passing of fluid around said valvesthrough said pressure-responsive device.

Another object of the invention is to provide a backowprevention unitincluding at least one check valve provided with means for indicatingmalfunctioning thereof.

Another object of the invention is to provide a pressure-responsivedevice for use in controlling the valves of a backflow prevention unitarranged so that no leakage can occur through said pressure-responsivedevice around said check valves from the property or consumers side ofthe line to the supply side of said line.

Another object of the invention is to provide a pressure-responsivedevice for controlling a backiiow prevention unit including diaphragmmeans subject to the pressure at the opposite ends of said unit andmeans for indicating leakage past and/or failure of said diaphragmmeans.

A still further object of the invention is to provide a backiiowprevention unit including a pair of check valves and a bleeder valvecommunicating with a space between said check valves and arranged todrain said space when the pressure upon the service or consumers side ofsaid unit becomes greater than that on the supply side of said unit, sothat reverse ow through the unit is prevented.

Another objectof theinvention isto provide a. backiiow prevention Vunitincludingy valves constructed so that they do not induce water hammer orline shock.

A still further object of the invention is to provide a backilowprotection unit including. fluid. pressure operated valve means at thesupply end.

of said unit at least and control meansfor said valve means including aportedJpilot. valve andy'- means between said ported pilot valve and uidpressure operated valve means for effecting a quicker opening andclosing of said fluid pressure operated valve means ithancouldwbeoobtainedby theuse :of :said pilot valve-alone..`

Stillanother. object of the-inventionisto Apro-- videnovel. controlmeans .for au backilow: prevention. unit which willeffect AbleedingoftheI unit in the event of,leakage past the--clieckvalve at-th serviceside -ofzthe unitand whichl .will also bleed' the.unit inthe event..thatal vacuum; condition occurs on the supply. side .of;the' unit..

A.'still further., object. off..the 'invention-.,isato provide backowxpreventiona .devices .that...are

adapted tosbe completelyassembled at the'factory,

shippedA in toto.: and readilynstalledin a .water supplymain: as anassembledunit.`

Other objects and advantages of the invention' will; be: apparent .from:the: following: .description taken in?- conjunction ::with:.` the t.accompanying Fig. :1, is afrontgelevationakview of:.a'.pr.eferred.fformrzofgb ackflow prevention ;unit: ,embodying two.,U

gate-type shutfoffvalves; one-,atgeach- .end1of; the

unit, a fpQwer; operated pilot-controlled"check valvev andanvautomatiecheck valve arranged in series-between -saidga-te.r valves;anautomatic. vacuum breaker valve -on `the-supply sidezof; thel unitbetween-,one ofthe gate valves andthepowerf operated cheekvalve,`a-pilot-controlled 'bleederA valve between the twovcheck-valves,-:and;autof` matic, pressure-responsive control means-foractuating-said ,pilot valve, all constructed andiarranged-inl accordancewithithe-principlesfofftheY 1 present invention;

Fig. -2 is a plan view-of thefbackflow prevention unit shownin Fig. l;

Fig.- 3 is an enlargedI sectionalviewthroughthe automatic vacuumbreaker,valve-takenon, therline- 3-3 of Fig. 1;

Fig. 4 is anV enlarged sectional viewthroughthe bleedervalve:takenaonathe line 4-4 of Fig. 1;

Fig. 5 is anenlarged longitudinalsectional View through the poweroperated check valve shown in Fig.- l;

Figs-Gis an enlargedlongitudinal-sectional view throughv--theautomaticcheek" Avalve shownl in Fig. 11 is a sectional detail view taken on theline lI-II of Fig. 10;

Fig. 12 is a sectional view taken on the line l2-I2 of Fig. 9 showingthe details of the pilot base;

Fig. 13 is a view of the pilot disc;

Fig. 14 is a sectional view of the pilot disc taken onthe line .Hf-I4 ofFig. 13;.

Fig. 15 is a view of the seat for the-,pilot disc;

Fig. 16 is a view of the pilot valve gasket;

Fig. 17 is a diagrammatic view illustrating the relative positions ofthe valves and control means of Ythe.backtlow prevention unitillustrated in Figs. 1 and 2 during a normal flow condition in the line;

Fig. 18'i's-ay diagrammatic view similar to Fig. 17 butt illustrating'the parts in the positions they assume during a static line condition;

Fig, 19 isa diagrammatic view similar to Fig. 17 but showing the parts.'of the unit in the positiorrthey. assume-whenzabackflovvlconditionfarises inl.the;yline Fig. 20is aidiagrammaticzview similaritoiFig-:.1 171. illustrating thez-partszirrrthe positions; they.- assumewhen. a .vacuum condition exists; inthe;

line;

Figi; 21.is-;a partly ydiagrammatic front eleva-.-

tional :view nof- Aanother. -form of- .backflow prevention`.'unitrinclu'dingv two.v 'power' operated;V check` valvesfarrangedftosimultaneously open and closeunder-the'. control lof apressure-responsive pilot` valvecontrol device;

Fig. 22 is a .diagrammaticView-ofI a vbackfllovv preventionunit similaritothat-shown in Fig. ;21.. but-includingl means between the pilot,valve, and power operated check valves toielect morefsensi'.

tive'fand :quick opening. and-.closing thereof-i and Fig.:-23fis.adiagrammatic view of. a'V backow prevention unitand control devicesimilar-to .thatshown in Fig. 1, but including means betweenrthe pilotvalve-and vthe'power operatedrchecknvalve tol effect-more sensitive.yand quickopening and4V closing thereof.

'lhe-.prererredV formof- `baclriiow. protectionwunit embodyingtlie-.pr-inciples of` thepresent inventiorr, is .illustrated in.i-Tfigs.- l to.. 20, inclusive.H

Referring first `to Figs. 1 and2, the -backflow pre-- vention. unit. is.generally identied.. by .thenumeral -I and includes. aconventional,manually operatedfgateor shut-offvalve- A theinletsideorwhiehisiconnected to a supply-pipe.X,-` shown indot-,andf-dasl. lines.rIheoutlet. side z of. the.- gate-.valve-.Ii.isV connected-.to one end.of..a pipe section 2 by a series of bolts 3,9@ conventional.4 gasket lbeinginterposed between.thegate-.valve Aandthe pipe section 2.

check valve B by bolts 5, a conventionalgasket- S beinginterposedvh-etweenthe valveB .andthe adjacent end of the pipe section 2..: Oneendof. a pipe nipple l (Fig. l) is connectedwith a boss onthe pipesection 2 and the opposite .end Ofsaid...

able gasket l2. being interposed between-the valve:

E and the pipe section lil. The-opposite end of the' pipesection. Hl iseonnectedwith the-inlet of an automaticy hydraulically loperated checkvalve Dbyboltshl, :a suitable. gasket. Mdbeing interposed bett-seen, thepipesection. Iiland said.

pipe nipple I5 (Figs. 2.and f 4) is threaded into a boss on one side ofthe pipe,..-

va-lve: One end c- The .oppositeend yof. the .pipe-section, 2 isvconnected withtheinlet of. a powerfoperated or-,uidfpressureoperatedsection l0 and the opposite end of said pipe nipple is connectedwith the inlet of a bleeder or backow indicator valve The outlet |36 ofthe Vbleeder valve E preferably communicates with the atmosphere inorder that the ow therefrom will provide visible evidence of a backowcondition in the line.

A `control device Z consisting of a, pressureresponsive device F, and apilot valve G actuated byxsad pressure-responsive device, isconveniently mounted upon the check valve D in a manner which will beset forth in greater detail hereinafter. However, it may be mentioned atthis point that the control device Z is arranged to automatically effectopening of the bleeder valve E and positive closing of the check valve Bwhenever the pressure at the inlet of the check valve B is less thanthat at the outlet of the check valve D.

The outlet side of the second check valve D is connected with the inletof a conventional gate or` shut-oir valve H by bolts I8, a suitablegasket I9 being interposed between the valves D and H. The'outlet sideof the gate valve H is connected with a service pipe Yy (shown indot-and-dash lines) `on the property or consumers side of the backflowprevention unit The vacuum breaker valve C is adapted to automaticallyopen and vent the supply pipe X to the atmosphere whenever the pressurein said pipe o is less than atmospheric pressure. The opening of thevalve C, of course, will prevent the creation of a vacuum condition inthe pipe X, which would normally tend to siphon water through the unit I'from the pipe Y into the pipe X.

`The automatic vacuum breaker valve C is best illustrated in Fig. 3, andcomprises two main housing sections J and 2|. The housing section2|lvincludes a threaded inlet 22 for the reception of the upper end ofthe pipe nipple 1, and a series of radially outwardly and upwardlyinclined arms 23 project from the outer surface of the inlet 22 to anannular flange 24. The ange 24 is provided with a surface 25 engagingone side of a flexible diaphragm 26 at the margin thereof. The .housingsection 2| has a similar surface 21 engaging the opposite side of themarginal poi'- tion of the diaphragm 26. The diaphragm 26 is clampedbetween the housing section 2| and the annular flange 24 and maintainedin assembledr relation therewith by a plurality of bolts 28.

The inlet 22 terminates at its upper end in an annular internallythreaded portion 29 adapted to receive a threaded portion 36 of a valveseat member 3 I. The upper end of the valve seat member 3| is preferablyinclined on an angle of about 5, to form a tapered seating surface, asindicated at 32.

A flat backing plate or disc 33 is disposed on the inner side of thediaphragm 26 and a valve disc 34 having a central, fiat-toppedprotuberance 34a is arranged upon the outer exposed side of `saiddiaphragm. The arrangement is very important because it permits freeiloating of the diaphragm 26 over about 85% of the area thereof betweenthe discs 33 and 34 and reduces buckling tendencies and providesiiexible, sensitive operation; The discs 33 and 34 are also made aslarge as possible consistent with the necessary flexing movement of thediaphragm 26 and the size ofy said diaphragm, and this is an importantfactor in distributing the lifting and sealing forces acting upon saiddiaphragm. The disc 34 is provided with an annular groove 35 in which anannular ber or plastic sealing member 36 is dishousing section 2| posed,said sealing member being non-adhering after long periods of contact andcooperable with the surface 32 of the seat member 3| to control theventing of the pipe X to the atmosphere through said seat member. Aclamping washer 31 engages the inner portion of the lower side of thesealing member 36, and a bolt 38 has its shank 39 extending through theplate 33, diaphragm 26, disc 34, and washer 31, and a nut 40 on saidshank secures the parts in assembled relation. Spacer means 39e in theform of one or more ber washers is disposed between the disc 34 andwasher 31 to permit the vnecessary clamping pressure to be applied tothe central portion of the diaphragm 26 without causing such distortionof the sealing member 36 as would result in faulty seating.

The housing section 2| is recessed to provide a chamber 4| for operatingfluid effective to ex the diaphragm 26 downwardly and thus urge thesealing member 36 into engagement with the seat 32, and a longitudinalpassage 42 in the bolt shank 36 establishes communication between theinlet 22 and the chamber 4|. The is also provided with a threadedopening 43 which is closed by a plug 44 when said housing section isused on a vacuum breaker valve instead of on a pressure iluid operatedvalve such as the ValveE', described later, in which case a conduit maybe connected with said opening. Obviously, the opening 43 and plug 44may be omitted when the housing section 2| is used on a vacuum breakervalve.

It will be apparent that the pressure in the pipe line X will becommunicated to the diaphragm chamber 4| through the pipe nipple 1 andpassage 42 in the bolt shank 39. So long as this pressure is aboveatmospheric, water will be introduced into the diaphragm chamber 4| andwill urge the sealing member 36 against its seat 32 to automaticallyclose the vacuum breaker valve C and prevent the flow of water to theatmosphere. However, should the pressure in the pipe X drop belowatmospheric pressure for any reason, then air at atmospheric pressureimmediately becomes effective upon the lower side of the diaphragm 26 toexpel the iiuid from chamber 4| via passage 42 and lift the` sealingmember 36 from its seat 32 and thus automatically vent the pipe X to theatmosphere to prevent the creation of a vacuum condition in said pipe.The opening of the valve C` is greatly facilitated by the fact that thelower end of the bolt shank 39 extends a substantial distance below theseat 32, thereby enabling the air rushing into the valve to rapidlySiphon the fluid from the chamber 4| and effect very body 45 having aninlet opening 46 and an out-v let opening 41 separated by a partition48. 'I'he partition 48 is provided with a threaded opening 49 for thereception of a seat 5D. 45 is further provided with a central opening 5|at its upper end surrounded by a annular boss The bodyA `section 13.

`52. .-Aseries of studs 53 is mounted in the boss T52.

i The valve B further includes an intermediate boss. 52. `A gasket 58 isdisposed between the flange 51 and the boss 52 and a series of nuts 59onthe studs 53 secures the intermediate section 54 to the body 45.

`The intermediate section 54 s provided at its upper end with a radiallyextending flange 60 which carries a series of studs 6|. These studsextend through a diaphragm y62 and a flange T63 formed on thecover 55.

A nut 64 threaded on each of the studs 6| clamps the marginal .portionof the diaphragm62 between the flanges 160 and 63 to thus secure thecover 55 to the intermediate section 54.

.The Ycover 55 is recessed to provide a dia- '.phragmchamber 65 attheupper side of the 'diaphragm62 adapted to receive operating fluid under'pressure to effect closing of the valve B. The central portion of thediaphragm 62 is :clamped between plates's and 61, a valve stern section68 extending through said plates and :diaphragm and'having a shoulder 69engaging the plate 61 and a threaded portion 10 adapted to receive'aself-locking nut 1| engageable with the plate'GB, whereby to maintainsaid valve ystem section, plates and diaphragm in assembled relation.The valve stem section 68 is provided with an axial passage 12 whichslidably receives the upper end of an auxiliary valve stem The auxiliaryvalve stem section 13 is shouldered as indicated at 14 and projectsthrough a'valve disc 15. The valve-disc 15 carries an annular sealingmember 16 which is cooperable with the seat 50 to cut off flow betweenthe inlet'chamber 46 and the outlet chamber -41 of the valve -B. Awasher 11engages the inner portion of the lower side of the sealingmember 16 to retain the same in place. The auxiliary'valve stem section13 extends through the washer 11 and a self-locking nut 18 securessaidvalve disc and washer to said auxiliary 4valve stem section. A suitablefiber washer 19 permits the necessary clamping pressure to be applied tothe disc and washer 11 4without undue distortion of the sealing member16. The lower. end of the -valve stem section =68 is adapted to engagethe shoulder 14 of the valve-stem section 13 to cause the member 16`tofengage the seat 50 when operating fluid under pressure fiexes thediaphragm 62 downdownwardly.

The intermediate valve section 54 includes a cylindrical wall'portion 8|which lies between theanges 51 and 60. The wall 8| is provided with oneor more vent openings 82 which lie immediately above the wall 56 andestablish comkmunication between the interior of the intermediate'valvesection 54 and the atmosphere. The wall 56 carries a gland 83 serving asa guide for the lower end of the valve stem section 68, said glandcarrying suitable packing 04 for preventing leakage along the outside ofsaid valve stem section. Additional packing 85, engaged by the lower endof the gland 83, serves to prevent leakage between the gland 83 and theadjacent surfaee of the wall 56. However, it will be-apparent that ifany liquid should leak along Ythe valve stem section 68 from the outletchamber 41 of the valve body B, or if any leakage should occur alongsaid valvestem from the diaphragm chamber 65, the same will flow out ofthe intermediate valve section 54 through the vent openings 82. It willalso be apparent that, if the diaphragm62 becomes ruptured, operatingfluid will discharge through the openings 82. Thus, the openings 82serve to indicate and reveal malfunctioning of the check valve B.

While the gland'83 serves as al guide for the lower end of the uppervalve stem section68, the upper end thereof is guided in a bushing 86 atthe lower end of a passage 81 in the cover 55, the passage 81 beingclosed at its upper end by a plug 88. The lower valve stem section 13 isguided in its movements by the walls of the passage 12 formedl in theupper valve stem section 68. Operating fluid isadmitted and exhaustedfrom the diaphragm chamber 65 through a passage 89 formed in any one ofa plurality of bosses 55a on the cover 55.

`It will be apparent that, with the foregoing valve arrangement, it isimpossible for any interchange of fluid to occur between the outletchamber 41 of the valve B and the diaphragm 65 of said valve. Instead,leakage from either of thechambers 41 and 65 is exhausted to theatmosphere through the vent openings 82, so that the arrangement servesas a means to positively prevent pollution of the water in the pipe X.

The automatic pressure-responsive check valve D is best illustrated inFigs. 6 and 7. The check valve D comprises abody 90, a cover 9|, and adiaphragm 92 arranged between said body and cover. A series of studs.93is mounted in the body 90 and each extends through the diaphragm 92 andcover 9| and receives a nut 94 for securing said body, diaphragm andcover in assembled relation. VThe body 90 includes an inlet opening orchamber 95 and an outlet opening or chamber 96 separated by partitionmeans 91 provided with an opening 98 establishing communication betweensaid inlet and said outlet chambers. A removable seat 99 is threadedlymounted in the opening 98 and is provided with a plurality of radialarms |00 which merge centrally and provide a guide |0| for the lower endof a valve stem 02. The upper end of the valve stem |02 is guided in abushing |03 (Fig. 7) mounted in the coverv 9 The valve stem |82 extendsthrough a central opening in the diaphragm 92 and carries a disc-likediaphragm supporting plate I 04 which engages a portion of the uppersurface of the diaphragm 92 and also carries a lower diaphragmsupporting member |05 which engages a portion of the lower side of saiddiaphragm. The member |05 has an inwardly projecting flange |06 at itslower side provided with an annular recess |01 in which an annularsealing ring |08 is adapted to rest and to engage the upper surface ofthe seat 99 when the valve D is closed to prevent all flow between theinlet chamber '95 and the outlet chamber 96. The valve stem |02 furthercarries a retainer plate |09 for maintaining the sealing ring |08 in therecess |01. vThe retainer plate |09 is engaged by an enlargement 0 onthe valve stem 02 and is clampingly secured against the sealing ring |08and is maintained in assembled relation with the diaphragm supportingmember |05 and the plate |04 by a self-locking nut which is Ymountedupon a threaded portion ||2 of the valve 'stem |02.

The cover 9| is recessed to provide a chamber ||3 above the diaphragm 92adapted to receive fluid under pressure for effecting downward iiexingof the diaphragm 92 to cause the sealing ring |08 to engage with theseat 99 and thus close the valve D.

The valve B is adapted to be controlled by the pilot valve G, as will beexplained more fully hereinafter, but the valve D is constructed so thatclosing thereof is automatically effected when the pressure in theoutlet opening 96 thereof is greater than that in the inlet opening 95.In order to accomplish such automatic operation, fluid for effectingclosing of the valve D is conveniently taken from the outlet chamber 98.Thus, the Valve D has a conventional elbow H4 (Fig. 2) threaded into atapped opening H5 in the side wall thereof in the zone of the outletchamber 96 and one end of a conduit H6 is com nected with said elbow,the opposite end of said conduit being connected by a conventionalfitting I with a boss 9|a formed on the cover 9|. The tting communicateswith a passageway H0 (Fig. 7) leading to the diaphragm chamber H3. Oneconduit I I6 may be suicient for certain installations, but in order tospeed up the operation of the valve D an additional conduit H9 isemployed. One end of the conduit |9 is connected by a conventionalfitting with a second boss 9|b on the cover 9| and a passageway |22establishes communication between the fitting |20' and the diaphragmchamber H3. The opposite end of the conduit H9 is connected by aconventional fitting |23 with a lateral opening |24 (Figs. 1 and 6) of aconventional four-way tting |25. One end of the tting |25 is connectedby a pipe nipple |26v (Fig. 2) with a tapped opening I2`| communicatingwith the outlet chamber 96 of the valve D. A test cock |28 is connectedby a pipe nipple |29 with the other end of the fitting |25. A secondtest cock |30 is connected toa nipple |3I communicating with the inletchamber 95 of the check valve D. The test cock |28 is adapted to beconnected by a conduit (not shown) with a source of pressure such as thetest cock 2 I3 communicating with the inlet of the gate valve A (at atime when the gate valves A and H are closed) to check the operation ofthe pilot valve G and to determine whether the check valve D isleaking.Interconnection of the test cocks |30 and 2|3 will check the operationof the bleeder valve E and also leakage through the check valve BLHowever, it will vbe understood that, alternatively, pressure gauges(not shown) maybe connected with the outlet of the test cocks |28 and|30, to obtain an indication of the pressure existing in the outlet andinlet openings 96 and 95, respectively, of the valve D, if desired. y y

It will be apparent from the foregoing,A that whenever the pressure inthe outlet chamber 96 of the` valve D exceeds that in the inlet chamber95, the outlet pressure will be communicated through the conduits I I6and H9 to the diaphragm pressure chamber lH3 vto eect downward exing ofthe diaphragm 92 with consequent downward movement `of the valve stem|02 to move the sealing ring I 08 into engagement with the seat 99 tocut off all ow through the valve. The design and construction of theauto` matic checkrvalve D is suchthat the differential pressure in theinlet and outlet openings 95 and 96, respectively, required to open orclose said valve does not exceed 1 lb. per square inch so'that verysensitive Valve operation is assured. Even under static flow conditions,that is, when the pressure in `the inlet chamber 9,5 substantiallyVequals thepressure in the outlet chamber 96, the

valve B will close because of the weight of the stem |02, member |05,etc., and the then greater elective area of the diaphragm 92 exposed tothe pressure of the uid in the diaphragm chamber H3.

The check. valve D always closes against the direction of normal flow,gradually, thereby eliminating all operating noise, hammering and lineshock. The closing rate of the valve D can be determined by the numberof conduits I i5 and ||9 employed and also by the internal diameter ofsuch conduits in order to admit operating fluid into the diaphragmchamber H3 at a predetermined desired rate. On the other hand, when thepressure in the inlet 95 exceeds that in the outlet (which is the normalcondition), the valve D will open gradually, and remain fully open solong as the inlet pressure is the greater.

The bleeder valve E is best illustrated in Fig. 4, and, as shown,includes a housing section |34 provided with a threaded inlet opening|35 for mounting the same upon one end of the pipe nipple I5 and anoutlet opening |36, which preferably communicates with the atmosphere.The housing section |34 also includes a radially extending flange |37which engages the marginal portion of one side of a iiexible diaphragm|38. A second housing section |39 engages the marginal portion of theopposite side of the diaphragm |38; the housing section |34, diaphragm|36 and housing section |39 being secured together in assembled relationby a plurality of bolts |46. A backing plate |4| engages one side of thediaphragm |38 and a valve disc |42 engages the opposite side of saiddiaphragm. The valve disc |42 carries a sealing ring |43 which isretained in place by a clamping washer |44. A bolt |45 extends throughthe plate |4 I, diaphragm |38, the disc |42 and washer |44, and a nut|45a is threaded on the bolt |45 to retain the parts in assembledrelation.

A seat member |46 is threaded into a neck |4'| formed in thehousingsection |34 inwardly of the inlet |35 and provides a beveled,annular seating surface |48 adapted to be engaged by the sealing ring|43 of the valve disc |42 to prevent ow through the valve E duringnormal operation of the unit The housing section |39 has a central boss|49 provided with a passage |50 communicating at its inner end with achamber |5| disposed at one side of the diaphragm 38 and adapted toreceive operating iiuid under pressure to normally maintain the valve Eclosed. The passage |50 has a conventional elbow tting |52 mountedtherein which is connected to one end of a conduit |53. The opposite endoi the conduit |53 is connected with the pilot valve G (Fig. 1) as willbe set forth hereinafter.

' The operation of the bleeder or backoW indicating valve E is notdirectly responsive tothe pressure in either its inlet |35 or itsoutlet. |36 but on the other hand, its opening and closing is controlledby the pilot valve G whose operation in turn is determined by thepressure-ressponsive control device F, which is actuated in accordancewith the pressure differential Iacross the check valves B and D, as willbe explained hereinafter. y

Referring nowy to Fig. l0, the pressure-responsive device F comprisesend housing sections |64 and I S5 and an intermediate housing section|66. The intermediate housing section |66 is annular and-,substantiallyU.-shaped in'cross-section, thus providing vspaced flanges and |I2` Aflexible

